In cellular radio systems, such as in WCDMA (Wideband Code Division Multiple Access) or UMTS (Universal Mobile Telecommunications System) systems information is transferred between a network device and a user, such as a mobile terminal, by transmitting signals.
These signals may be distorted on their way from a transmitter to a receiver. Thereby e.g. a modulator of a transmitter, means of transmission, i.e. radio waves, interference sources, fading and demodulator of a receiver have distorting influence on the signals. These factors form a so-called channel. Each base station has a plurality of channels at its disposal. On each channel information is transferred between the base station and the users, thus establishing a connection between a user and the base station. The base station decides whether to admit new users depending on the number of such connections or on the workload of the network. This process of decision is called admission control.
In WCDMA power based admission control can be used in both, uplink and downlink. In uplink there is a cell based threshold for received channel power level. Correspondingly in downlink there is a cell based threshold for transmitted channel power level. These thresholds are used to determine whether to admit a new user or not.
Accordingly these threshold values are used to determine how much traffic is allowed in a cell of the cellular radio network. Thereby it is important to select the correct thresholds. If the threshold values are too low, not all of the capacity of the cellular radio network is utilized. On the other hand, if the threshold values are too high, too many connections are admitted in a particular cell. Thus, the interference increases causing bad quality of the connections between the users and the network, in particular of calls. This is caused by power outage of mobile terminals in uplink and in downlink connections that hit the maximum specific transmission powers, reducing the coverage of the specific cell and making the quality of calls worse.
It is known to manually set threshold values network parameters by choosing a default value. This value is determined for default conditions, i.e. the typical conditions of a network cell are established and the parameter value is chosen to optimize these conditions. Hence the default value is a suitable choice, if the local network conditions correspond largely with the default conditions. But in general the local network conditions differ substantially from the default conditions. Furthermore the optimal setting for a network parameter may change in time. This is particularly true for parameters that are related to propagation conditions for radio waves in a cell or the load of the specific cell. It is known to manually correct the threshold values. However, as the number of cells in a network is very high, in particular more than 10,000, manual correction is a very time-consuming and difficult task.